1. Field of the Invention
The present invention relates to a high-pressure treatment apparatus for feeding an object to be treated such as, for example, wood waste (including construction waste material), paper, food waste into a high-pressure atmosphere by means of a screw feeder to treat it under high pressure and a method for operating the high-pressure treatment apparatus.
2. Description of the Related Art
Recently, waste (waste material) of wood, agricultural products, food, sludge, paper and so on, for example, is used as a raw material of biomass, and its applicability, for example, as fuel to generate power is under consideration by reforming it to improve its quality as fuel by bringing it into contact with, for example, water in a subcritical state. The reforming reaction is performed by feeding a raw material of biomass, for example, granular or block wood waste into a reaction container which is filled with, for example, high-temperature and high-pressure hot water and bringing the wood waste into contact with the hot water. It is conventionally known that a slurry pump, a screw feeder, a rotary feeder, and a vibrating feeder are used as means for feeding an object to be treated into a reaction container in such a high-pressure state (Refer to, for example, Patent Document 1.).
(Patent Document 1)
Japanese Patent Application Laid-open No. 2000-189781 (P. 14, FIG. 11)
An apparatus configuration in the case in which a screw feeder is used as the above-described feeding means to feed wood waste, for example, will be briefly described using FIG. 6. A numeral 10 in the drawing denotes a reaction container for reforming wood waste, for example, in which high-pressure and high-temperature hot water is filled. A numeral 11 denotes a screw feeder for feeding the wood waste into the reactor 10. The screw feeder 11 comprises a casing 12 constituting a main body portion and a screw mechanism 13 provided in the casing 12 for conveying the wood waste by rotation, and is configured to receive wood waste thrown into the casing 12 via a hopper 14 connected to one end side of the casing 12 and discharge it from the other end side of the casing 12, thereby feeding it into the reaction container 10.
However, in the case of using a slurry pump as the aforementioned feeding means, the pump has a problem that it cannot convey the wood waste unless the wood waste is mixed with water into a slurry state thus its mechanism fails to feed the wood waste into the reaction container 10 in a high density state with little water, and increases cost because of a large amount of heating required to change the water mixed with the wood waste into hot water. On the other hand, when the screw feeder, rotary feeder, or vibrating feeder is used, the feeder can convey the wood waste in a high density with little water, but it is difficult for these feeding means to pressure-feed the wood waste toward a high-pressure side in a large pressure difference. In the example illustrated in FIG. 6, for example, the hot water in the reaction container 10 may flow back into the screw feeder 12 unless an opening/closing mechanism 15, for example, is provided between the screw feeder 12 and the hopper 14 to equalize to some extent pressures before and after the screw feeder 12 in order to maintain the back pressure of the screw feeder 12. This leads to complicated apparatus configuration and causes another problem that it is difficult to control the opening/closing action of the opening/closing mechanism 15 so as to prevent the hot water from flowing back for continuous feed.